Stablization and protection of hydrocarbon compositions



. 24, 4 M. c. K. JONES 2,303,050

STABILIZATION AND PROTECTION OF HYDROCARBON COMPOSITIONS 'Filed Oct. 31,1940,,

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atented 24, 1942 STABLIZATIGN AND PROTECTKON 01F HYDROGARBONCOMPOSITIONS Minor 0. K. Jones, Westfield, 'N. 3., assignor to StandardOil Development Company, a corporation of Delaware Application October31, 1940, Serial No. 363,665

7 Claims.

This invention relates to a method 'of protecting hydrocarboncompositions, particularly of the nature of light hydrocarbon distillatefuels.

One of the objects of this invention is to provide a method ofpreserving stability of the hydrocarbons during storage and use. Afurther object is to protect highly volatile hydrocarbon compositionsagainst fire hazards.

A substantial removal of air from a hydrocarbon composition followed bysaturation of the composition with carbon dioxide under moderateconditions before storing provides a practicable method of insuringprotection to the hydrocarbons. When the hydrocarbon compositions arethus treated, they do not have to be kept in any special type ofcontainer nor under elevated pressures nor at lowered temperatures togive the desired advantages, but need be handled only with the usualprecautions.

When a hydrocarbon composition, such as a motor fuel or even a higherboiling petroleum distillate is exposed to air or oxygen it has atendency to'absorb these oxidizing gases, which when present even invery minute quantities, cause considerable deterioration with resultantacidity formation, gum formation, discoloration, etc. For example, whena -gallon case of conventional type used for transporting fuel is filledwith gasoline even to full capacity leaving no air space and is tightlycapped, a progressive deterioration of the fuel in the container can bedetected. Moreover, it is diflicult and impracticable to store a highlyvolatile fuel in any economical type of container without leaving somegas space for expansion. Therefore, ordinarily, the hydrocarbon liquidcomposition is exposed to oxygen in this gas space- Even those amountsof oxygen which are normally occluded or absorbed in the hydrocarbon oilitselfare present in a suflicient amount to give undesirabledeterioration.

Hitherto it was found diflicult and expensive to remove the air oroxygen which tends to be dissolved or otherwise taken up and retained inthe fuel during the refining processes. The hydrocarbon liquidsmaynormally contain as much as by volume of absorbed air. and even withpainstaking efiorts to saturate the aircontaining hydrocarbon liquidswith large volumes of carbon dioxide at low temperatures, a

point is reached at which the hydrocarbon liquid continues to retain asubstantial amount of the absorbed air.

It has now been found possible, in accordance with the present'invention, to free the hydrocarbon liquids of the absorbed air byplacing the liquids under vacuum with convenient operating conditions,and subsequently while in the deaerated condition to eflicientlydissolve into the hydrocarbon liquids gaseous carbon dioxide. In first'deaerating the hydrocarbon liquids under vacuum, the amount of absorbedair can be reduced to a mere trace or negligible amount, for example ofthe order of less than 1% by volume to 0%. In this deaerated condition,the hydrocarbon liquids substantially free of dissolved gas can bereadily charged with gaseous carbon dioxide until they contain, undernormal conditions, from about 100% to 300% by volume of the carbondioxide and retain only a negligible amount of air or oxygen. Bycarrying out this treatment, it was found that the storage stability ofa liquid hydrocarbon composition, such as a motor fuel, is greatlyimproved, even though the liquid is kept in a container at ordinaryatmospheric pressure and temperature. The step of first deaeratingallows a suitable proportion of the carbon dioxide to be readilydissolved in the hydrocarbon liquid without imparting to the compositionan excessive vapor pressure, hence the composition containing thedissolved carbon dioxide is satisfactorily stable under ordinaryconditions with the usual type of handling.

It has also been found that the highly volatile hydrocarbon fuels thustreated are highly benefited by a substantial increase in their flashpoints over a considerable period of time, even if the fuels are placedin a common type of fuel craft or automobiles.

exist when the carbon dioxide is present in the supply tank vented tothe atmosphere. This added protection of the fuel is advantageous whenthe fuel is carried in supply tanks of air- Under the conditions thatume of carbon dioxide charged in the deaerated liquid hydrocarboncomposition. More than this proportion requires refrigeration of thecomposition to low temperatures, and even though an aviation gasolinefuel contained considerably in excess of 300% by volume of carbondioxide, the fuel showed a low flash point, particularly when the fuelwas not first deaerated. For example,

an aviation gasoline saturated with carbon diox-' ide at 22 F. showed aflash point of -35 F. with a closed Tag tester. Numerous otherdifliculties are encountered in treating and storing a fuel which is notpreliminarily deaerated, and which is charged with carbon dioxide at lowtemperatures, e. g., expensive refrigeration, large waste of carbondioxide, expensive and compli cated equipment for storing, anddifficulties in with decrease in pressure the carbon dioxideconcentration tends to decrease. in the following table:

, TABLE I Effect of altitude on. CO2 solubility in gasoline This isillustrated Solubility of CO: in

gasoline Elevation 0.] liter 20,000.. I. .II

It is to be noted that the net efiect of the change of altitude is thatthe concentration of the carbon dioxide remains nearly constant. Ac-

cordingly, the carburetor and fuel inductionmeans of the engine do notneed alteration in adjustment after they have been set for the carbondioxide protective fuel herein indicated.

A method by which a hydrocarbon composition is satisfactorily deaeratedand treated with carbon dioxide will be described by reference to theaccompanying drawing. The drawing shows a diagrammatic 'view inelevation and cross section of apparatus suitably used for the method.

Referring to the drawing, l indicates a vacuum or deaerating tower. Thistower may be con structed similarly to conventional dephlegmating towersin refiniery equipment. In the tower may be disposed baflle plates 2, asshown, for the purpose of preventing entrainment of hydrocarbon oil inthe gases removed overhead through line 3 and of extending the surfaceof the oil so as to facilitate the disengagement of the air. The fuel tobe treated is passed in near the top of the tower by line 4.

At the top of the tower l is provided a cooling means in the form of acondenser or jacket to chill the gaseous fluids as they are withdrawnfrom the tower through packing I. The cooling medium in the coolingmeans may be a slurry of solid carbon dioxide, or any other materialwhich has a low temperature, e. g. cold brine, or even cold water. Thecooling medium is conducted through the unit by pipe 8. It is, however,desirable to have the gases passing the cooling means reduced to afairly low temperature to prevent passage of light hydrocarbon vaporsfrom the oil overhead. Of course, less cooling is required if the oiltreated has low volatility, as this cooler is only to insurecondensation of any hydrocarbons which might tend to boil under thereduced pressure. The overhead line 3'from the deaerating tower, isevacuated by means of a vacuum pump 6. For extra precaution ineliminating any loss of hydrocarbon vapors, the gaseous fluids may bepassed by the vacuum pump on the pressure side into a heat exchangecondenser 9 in which overhead vapors of normally liquid hydrocarbons arecondensed under pressure at low temperatures, so that a furtherseparation of gases from condensible vapors is obtained, the gases beingwithdrawn from the receiver ill by line H. Any condensate formed incondenser 9 and collected in receiver it may be recycled to tower l byline I12, or be withdrawn from the system through valved outlet l3.

From a point near the bottom of tower I, the deaerated hydrocarbon oilis made to pass by pump 26 through line 21 to enter the upper part I ofthe absorption tower M. Near the bottom of the absorption tower carbondioxide gas is fed by line M5 to pass countercurrently to the stream ofthe hydrocarbon oil as it descends through the tower. Baille plates llprovided with bell caps and down corners B8 are disposed in tower M toaid in bringingabout intimate contact between the carbon dioxide gas andthe hydrocarbon oil so as to facilitate the absorption. The unabsorbedcarbon dioxide gas withdrawn from the towerby line it through packing 20in a cooler 2! may be recycled to the inlet line is by means of thecompressor 22. A supply of fresh carbon dioxide is led in by line 23.

The fuel saturated with the carbon dioxide is withdrawn from the towerby valved outlet 24 which acts as a line for charging a container 25 inwhich the oil is to be stored. I

The storage container or packing case to be filled with the treated oilis preferably first filled with carbon dioxide, injected by valvecontrolled line it from supply line 23, so that this gas displaces allair from the container, and in turn, the carbon dioxide is displaced bythe treated fuel as it is charged into the container. After thecontainer is filled to the desired level, it may be-capped orhermetically sealed; or it may be left open to atmospheric pressurethrough a suitable small vent.

In the step of deaerating the hydrocarbon liquid, the vacuum or reducedpressure to which the liquid is subjected depends to some extent on theemciency of the deaerating apparatus, i. e. such factors as the time inwhich the liquid is subjected to the vacuum, and the extent to which theliquid is agitated and spread out to give greater liquid-gas interphasearea. The reduction of pressure also depends to some extent on thetemperature of the hydrocarbon liquid, for at higher temperatures moreair can be disengaged with less reduction in pressure. However, as apractical matter, the temperature should not be very high, for itbecomes more diflicult with increase in temperature to cool the overheadgases and to prevent loss of volatile normallyliquid hydrocarbons.

deaerating of aviation gasolines are tempera- Conditions in the vacuumtower found to .be suitable for obtaining eflicient tures in the rangeof 40 F. to 100 F. and a subatmospheric pressure of 2 to 200 millimetersof mercury absolute, more preferably 55-75" F. and 25 to 100 mm. Hgabsolute.

In the absorption tower, the temperature of the liquid contacted withthe carbon dioxide is suitably at about ordinary atmosphere or roomtemperature, for it is preferred not to have the liquid highlysupersaturated with carbon dioxide nor too cold when it is being chargedinto the container. A suitable temperature range for the absorption isabout 40 F. to about 70 F. The pressure in the absorber may beapproximately atmospheric or superatmospheric up to about 5 atmospheres.

In the preferred embodiment described, the deaerating step is carriedout with very little expense. The carbon dioxide absorption step alsohas a high efficiency, for it permits the carbon dioxide to be recycledwithout deleterious contamination by oxygen and the absorption processhas a high efliciency due to the intimate contact of the carbon dioxidewith the hydrocarbon liquid. The operation described also permits thehydrocarbon liquid to be treated with very little or substantially noloss of normally liquid hydrocarbons, even when these hydrocarbons arehighly volatile, as for example, a gasoline fuel having an initialboiling point of about 100 F.

To demonstrate the effectiveness of the present method for imparting toa volatile gasoline a safety fuel flash point, analytical determinationswere made on a sample of a regular aviation gasoline before and afterbeing subjected to the described treatment of deaerating and saturatingwith carbon dioxide. Tests were made by the A. S. T. M. method with botha closed flash point tester and a Tag open flash point tester. Theboiling ranges and octane numbers of the treated and untreated gasolinewere as follows:

TABLE II Inspection of clear aviation gasoline The distillationcharacteristics of the motor fuel were not appreciably changed. It wasdemonstrated, however, that the flash point of the fuel was greatlyelevated, as is shown in the following data:

TABLE III Aviation gasoline deaerated and Aviation saturated with carbondioxide gasoline l0 Did not "flash up to 140 F. Vapors burned outsideopening from about 70 to 140 F. Burned above tester at Flash point (tagclosed testcr).

Similarly, a kerosene distillate of standard specification was treatedand tested for flash point in comparison with the flash point test of asample of the untreated kerosene to obtain the following data:

method of treating hydrocarbon liquids that has been described isapplicable to all typesofliquid hydrocarbon refinery products, it is ofparticular benefit for treatment of motor fuel distillates such asgasoline, kerosene, Diesel fuels, and heating oils. It may also be usedin protecting viscous liquid to solid hydrocarbon products which aresusceptible to oxidation.

One of the highest advantages of the present invention is that itprovides a protected hydrocarbon composition which is substantially freefrom deleterious absorbed oxygen and containing absorbed carbon dioxidein suitable and adequate amounts incorporated into the oil by absorptionwithout excessive cooling or supersaturation so that the treatedcomposition can be readily and safely stored in ordinary containersunder normal conditions.

The safety aviation fuel made possible by the present inventionconsiderably reduces the fire hazard incident to forced landings shouldgasoline he spilled over hot engine parts. It is well recognized thatfire following an airplane accident is a frequent cause of the resultantfatalities, a condition avoided by the present invention. In addition,military aviation gasoline treated as described would be less vulnerablein the face of enemy attack.

In treating aviation fuels by the present method, it was found that theywere converted into excellent safety fuels having substantiallyunchanged volatility and anti-knock characteristics without imparting tothe fuels excessive vapor pressure properties, which would beundesirable in causing vapor lock. Safety fuel compositions thusprovided preferably have boiling ranges substantially within the rangeof F. to 350 F., boiling off at least 50% at normal pressure up to about212 F., and have satisfactory low Reid vapor pressures in the range ofabout 7 to 8.5 pounds per square inch at 100 F. These treated safetyfuels are made substantially free of deleterious oxygen by thedeaeration and contain suflicient stably dissolved carbon dioxide, in aproportion of 100% to 300% by volume under normal conditions, to elevatethe flash point of the fuel to as high as F. and to ordinarily maintainthe flash point above 70 F. for a long period, as determined with aTagliabue closed fiash point tester.

It is not intended that the invention be limited by the specificexamples and embodiments given for the purposes of illustration, for anumber of modifications come within the spirit and scope of theinvention as set forth in the appended claims. I

I claim:

1. A safety motor fuel composition of high oxidation resistance and highflash point which comprises a gasoline hydrocarbon boiling substantiallywithin the range of 100 F. to 350 F.

substantially free from molecular oxygen and v below 8.5 pounds persquare inch at 100 F.

2. A motor fuel composition of high oxidation resistance and high flashpoint, which comprises a gasoline hydrocarbon fuel deaerated to reduceits air content to a negligible amount, and containing dissolved carbondioxide in a proportion of about 100% to about 300% by volume underatmospheric conditions of temperature and pressure.

3. The method of improving a safety motor fuel composition to increaseits resistance to oxidation and elevateits flash point, which 'comprisessubjecting a highly volatile gasoline hydrocarbon composition of whichat least 50% boils off at 212 F. to a subatmospheric pressure underconditions to substantially deaerate said composition, and dissolvinginto said deaerated composi tion under approximately atmospherictemperature and pressure gaseous carbon dioxide until said compositioncontains from about 100% to 300% by volume of dissolved carbon dioxide.

4. The method as described in claim 3 in which said hydrocarboncomposition is deaerated at an absolute pressure in the range of fromabout'2 to 200 millimeters of mercury and a temperature in the range offrom about 40 F. to about 100 F.

5. A method of treating a hydrocarbon distillate productto stabilize andprotect the product during storage, which comprises applying to saidhydrocarbon distillate product a subatmospheric pressure underconditions to disengage substantially all absorbed air, and thereafterintimately contacting the thus deaerated hydrocarbon product with astream of gaseous carbon dioxide at about atmospheric temperature andpressure until said hydrocarbon product contains from about to 300% byvolume of dissolved carbon dioxide.

6. The method as described in claim 5, in which said deaeratedhydrocarbon product is intimately contacted with a stream of gaseouscarbon dioxide to cause absorption of the carbon dioxide by thehydrocarbon product, and unabsorbed carbon'dioxide from said streamsubstantially free of oxygen is recycled into contact with the deaeratedhydrocarbon product.

7. In the refining of a liquid hydrocarbon product susceptible todeterioration by oxidation, a step in the treatment which comprisessubjecting the hydrocarbon product to a degasifying treatment underreduced' pressure for removing substantially all normally gaseoussubstances including air absorbed and occluded in said liquid product,then substantially saturating the degasified liquid hydrocarbon productwith, carbon dioxide under approximately atmospheric temperature andpressure until at least about 100% by volume of carbon dioxide isdissolved in the liquid hydrocarbon, loss of 'any normally liquidhydrocarbons volatilized during the process being prevented bycondensation.

. MINOR C. K. JONES.

